A variety of transmission systems and methods exist for powered equipment such as, for example, mowers, tillers, snowmobiles, and other motor-driven apparatuses. Continuously variable transmission (CVT) systems, also known as infinitely variable transmission systems, can be used to continuously vary the transmission ratio and can provide both forward and reverse drive operations with speed control. CVT systems can be friction CVT systems, hydrostatic CVT systems or ratcheting CVT systems. Friction CVT systems can include a variable speed first wheel that can be a pulley that can be rotated, directly or indirectly, by an engine motor. A second wheel can be laterally movable along a shaft and positioned orthogonally with respect to the first wheel. The second wheel can frictionally engage the first wheel such that rotational movement of the first wheel, as driven by the motor, causes rotational movement of the second wheel. The second wheel can be coupled to the shaft such that rotational movement of the second wheel causes rotational movement of the shaft. An axle to which tires are attached can be interconnected to the shaft such that rotational movement of the shaft rotationally moves the tires. The ability of the second wheel to move laterally on the shaft allows the second wheel to engage the first wheel at different locations to thereby control the speed of the tires in a forward or reverse drive operation.
Up to now, the shaft of such systems has had to be of a shape other than round, for example such as hexagonal, in order to transmit torque from the rotatably driven second wheel to the shaft. A rubber edged disk has been used with a centrally positioned bore of a shape, such as hexagonal, to couple with the shaft to allow lateral movement of the second wheel and prevent rotational movement of the second wheel on the shaft.
In light of the above, there remains room for improvement in linearly adjustable torque transmission systems and methods.